When during the drilling of an oil well the bit penetrates an earth formation having an unexpectedly high pressure, the hydrostatic head of the drill mud standing in the well may not be sufficient to prevent formation fluids from entering the bore hole and traveling upward toward the surface. If such flow is not controlled quickly, a "blow out" of the well can occur and create very serious safety hazards to personnel working on and around the drilling rig. Of course a resulting fire can cause tremendous damage to the drilling equipment. At first indication of possible blow out conditions, the blow out preventers can be closed around the drill pipe to seal off the annulus. If the kelly by which the drill pipe is driven happens to be attached to the upper end of the string of drill pipe, a valve may be present in the system which can be closed to shut off upward flow through the drill pipe itself.
However, should upward flow begin while the kelly is not connected to the drill pipe, for example while a threaded connection between pipe sections is being made, a very hazardous situation is presented for which applicant knows of no adequate apparatus available to quickly and conveniently control the flow. U.S. Pat. No. 4,026,354 issued May 31, 1977 shows a somewhat massive device that is lowered over the open end of the pipe by a crane or a boom and operated by a long drive shaft that extends through a kill line in order to make a connection with the pipe and enable a shut-off valve to be closed. Due to its massive nature, this device could not be positioned and put into operation as quickly as would obviously be desirable under the circumstances. U.S. Pat. No. 3,625,282 issued Dec. 7, 1971 shows a device having a clamp that mates only with a special type of groove arrangement on the upper end of the casing, the clamp having bolt holes that can be aligned with matching holes on the lower flange of a spool which mounts a master valve. The clamp and spool have an offset hinge bolt to enable the spool to be pivoted into position. However this apparatus requires the make up of numerous bolts before complete attachment can be accomplished, which is time consuming and thus potentially dangerous, and the clamp assembly is designed for attachment only to a specific type of machined end fitting.
It is the general object of the present invention to provide a new and improved safety apparatus that can be quickly and conveniently attached to the upper end of the drill pipe or similar conduit and which enables a valve to be threaded into the pipe and then closed to prevent upward flow.